Table 1.

Binding to the RG and R⁰ Conformations of Human PTHR1^a

	IC50 (nM)
	R0				RG
		n	p versus			n	p versus
			PTH(1‐34)	PTHrP(1‐36)			PTH(1‐34)	PTHrP(1‐36)
PTH(1‐34)	10.4 ± 3.7	8	1.00	0.67	0.16 ± 0.08	8	1.00	0.30
PTHrP(1‐36)	8.20 ± 3.41	3	0.67	1.00	0.07 ± 0.01	3	0.30	0.30
M‐PTH(1‐11)/PTHrP(12‐36)	2.14 ± 0.47	3	0.06	0.22	0.55 ± 0.15	2	0.17	0.19
M‐PTH(1‐14)/PTHrP(15‐36)	2.69 ± 0.99	3	0.08	0.24	0.67 ± 0.05	3	0.0006	0.0064
M‐PTH(1‐17)/PTHrP(18‐36)	1.91 ± 0.39	4	0.06	0.20	0.23 ± 0.02	4	0.42	0.00
M‐PTH(1‐18)/PTHrP(19‐36)	1.66 ± 0.22	4	0.05	0.19	0.13 ± 0.02	4	0.72	0.02
M‐PTH(1‐22)/PTHrP(23‐36)	7.80 ± 2.55	3	0.58	0.93	0.67 ± 0.02	3	0.0004	0.0001
M‐PTH(1‐26)/PTHrP(27‐36)	1.73 ± 0.75	5	0.05	0.19	0.13 ± 0.04	5	0.73	0.21
M‐PTH(1‐30)/PTHrP(31‐36)	2.98 ± 0.48	4	0.09	0.26	0.21 ± 0.03	4	0.60	0.013

Equilibrium competition binding reactions were performed either in the presence (R0) or absence (RG) of GTPgammaS, and RG reactions used membranes from cells transfected with a high‐affinity GαS‐dominant‐negative mutant in addition to the PTHR1. Data are means ± SEM of the number of experiments indicated by n; p = Student's t test versus PTH(1‐34) or PTHrP(1‐36).

^aIC₅₀ values are peptide concentrations (nM) that resulted in 50% inhibition of binding of ¹²⁵I‐labeled PTH(1‐34) radioligand (R0) or ¹²⁵I‐labeled M‐PTH(1‐15) radioligand (RG) to the hPTHR1 expressed in membranes of transiently transfected COS‐7 cells.